The block follows reports that authorities in Panama, the Dominican Republic and Australia have found diethylene glycol, a compound used in anti-freeze and known to have been a source of a number of mass poisonings, usually from adulterated medicines.
The FDA said that it was blocking all consignments of toothpaste at US borders and would not be releasing any of it until tests show that it is categorically safe.
A spokesman for the FDA told US reporters that there had been no evidence that any tainted products had entered the US market, but that sampling of all shipments of toothpaste had been made a 'top priority'.
The two biggest toothpaste manufacturers in North America - Procter & Gamble and Colgate-Palmolive, have both said that they will not be affected by the block, as none of their toothpastes are currently imported from China.
In fact the FDA believes that the ban will mainly affect gray market imports from China, which are often sold in the North American market illegally.
The same chemical is said to have recently been found in cough medicine in Panama, a problem that has led to the deaths of 50 people there.
The China government said that a team from its agencies was currently investigating the alert over the toothpaste exports. According to a BBC report the team was focusing its investigations on the eastern province Jiangsu and Beijing.
The scare highlights the ongoing problem with the gray market in China, which has led to a number of major incidences over the past few years. In March this year, pet food ingredients from China contained a chemical that killed pet cats and dogs in the US.
There is also a continuing problem of cosmetic counterfeiting, a major challenge in the North American market, where fake imports continue to pour in from many Asian markets, namely China.
