The move by the US shoe-makers comes in the wake of concerns that doctors and nurses wearing Crocs could be injured if instruments or needles fell through the holes. Also some apprehend that the static electricity generated by generate could knock out medical equipment.
"With the introduction of workplace-geared designs, we are further expanding our footwear offerings to provide functional, high-comfort footwear without holes to meet a high level of compliance in workplace environments," said Ron Snyder, CEO of Crocs.
The colourful, rubberized clogs or shoes are extremely popular among nurses in North America in general.
But in region after region, another they are being banned. "Crocs can kill," screamed the front page of the UK tabloid The Sun last Wednesday. The paper reported the banning of the shoes by some Sheffield hospitals, following static electricity concerns.
There are also a flurry of reports that unwary Crocs-shod children get their feet mangled in escalators.
One of the largest subway systems in the US -- the Washington Metro -- has even posted ads warning riders about wearing such shoes on its moving stairways. The ads feature a photo of a crocodile shoe, though they don't mention Crocs by name.
Four-year-old Rory McDermott got a Croc-clad foot caught in an escalator last month at a mall in northern Virginia. His mother managed to yank him free, but the nail on his big toe was almost completely ripped off, causing heavy bleeding.
According to reports appearing across the United States as also in Singapore and Japan, entrapments occur because of two of the biggest selling points of shoes like Crocs: their flexibility and grip. Some report the shoes get caught in the "teeth" at the bottom or top of the escalator, or in the crack between the steps and the side of the escalator.
The reports of serious injuries have all involved young children. Crocs are commonly worn by children as young as 2. The company introduced shoes in its smallest size, 4/5, this past spring.
"Thankfully, escalator accidents like the one in Virginia are rare," the company said in a statement.
In Japan, the government warned consumers last week that it had received 39 reports of sandals -- mostly Crocs or similar products -- getting stuck in escalators from late August through early September. Most of the reports appear to have involved small children, some as young as two years old.
Kazuo Motoya of Japan's National Institute of Technology and Evaluation said children may have more escalator accidents in part because they "bounce around when they stand on escalators, instead of watching where they place their feet."
In Singapore, a 2-year-old girl wearing rubber clogs -- it's unclear what brand -- had her big toe completely ripped off in an escalator accident last year, according to local media reports.
And at the Atlanta airport, a 3-year-old boy wearing Crocs suffered a deep gash across the top of his toes in June. That was one of seven shoe entrapments at the airport since May 1, and all but two of them involved Crocs, said Roy Springer, operations manager for the company that runs the airport terminal.
One U.S. retailer that caters to children, Mattel subsidiary American Girl, has posted signs in three locations directing customers wearing Crocs or flip-flop sandals to use elevators instead of escalators.
During the past two years, so-called "shoe entrapments" in the Washington subway have gone from being relatively rare to happening four or five times a week in the summer, though none has caused serious injuries, said Dave Lacosse, who oversees the subway's 588 escalators, the most of any U.S. transit system.
The U.S. Consumer Product Safety Commission said escalator accidents caused more than 10,000 injuries last year, but the agency has few records of specific shoe problems. Only two shoe entrapments have been reported by consumers since the beginning of 2006. One reported in May involved "rubber footwear."
Agency spokesman Ed Kang urged people who have had problems to report them on the commission's Web site.
But Crocs, says that the shoes are being targeted unfairly. "We are so popular now and get a lot of attention, so it's kind of logical that these kind of claims are made," said Liselore Stuut, a Crocs spokesperson. "But these things happen with all shoes, not only Crocs."
Mike O'Neill, a foot surgeon and spokesperson for the Society of Chiropodists and Podiatrists, says that wearing appropriate shoes in surgery is important, and not just to prevent the build-up of static. "You get a lot of spillage in theatre," he says. "Orthopaedic surgeons wear Wellington boots. So do many gynaecologists -- the last thing you want is to have a pregnant woman saying, 'My water's broken,' and you tell her 'Yes, I know, it's just gone through the holes in my Crocs'."
The company promises to look more closely at the "static" claims. But it insists that there is no evidence to suggest that the shoes behave differently to any other rubber-soled footwear. It has even commissioned a report that says that Crocs pose a lower risk of static build-up than other shoes.
Indeed, a spokesman for Sheffield Teaching Hospitals said that the trust had banned Crocs not in response to the alleged static risk (there are no reported incidents of Crocs disrupting medical equipment in the UK) but because the shoes contravened dress code.
If other NHS trusts follow suit, thousands of medical staff who have come to swear by Crocs for their comfort will surely protest. The shoes' feather-light, anti-microbial footbeds have made them a hit in hospitals, especially with nurses, who can cover up to five miles in a shift. But are Crocs good for the feet?
"They have shortcomings," says O'Neill. "They're disastrous if they're the only shoe somebody standing for a long period is going to wear. You really need something that is measured for the foot. The problem is Crocs do not provide enough support -- they rely on the foot sliding forward as far as it will go."
O'Neill says that Crocs are better suited to holiday wear. "They're brilliant on the beach or round the pool, mainly as a much better alternative to flip-flops, which are terrible for feet. They have no heels, which causes the foot to roll inwards, potentially causing serious ligament and tendon damage. Crocs at least have a slight heel and a strap to keep them on the foot."
Whether or not there is any validity to the claims against them, Crocs show no sign of losing popularity. Started in 2002 by a pair of American sailors looking for the ideal deck shoe, Crocs has sold more than 20 million pairs of shoes in the past 12 months -- and come winter, the West will see the arrival of Croc Mammoths, a fur-lined shoe that could become another super hit.