Thai police on Monday found 400 boxes of bomb-making materials in a shop believed to be linked to a plot to carry out terrorist attacks.

The materials - urea and ammonium nitrate - were found packed in electric fan boxes in a building 35 kilometers south-east of Bangkok, days after the U.S. embassy warned of possible attacks on tourist sites in the capital.

Police were alerted to the cache by a Swedish-Lebanese man arrested Friday on suspicion of being a member of the Hezbollah militant group.

Attis Hussein, wearing a hood to protect his identity, guided more than 100 police to the shophouse in Samut Sakhon town Monday morning.

"The suspect told us the bomb-making materials were not for terrorist attacks in Thailand, but were intended to be smuggled out of the country," national police chief Priewpan Damapong said.

It was not clear whether Hussein faces charges in Thailand or will be deported, Bangkok police commissioner Lieutenant-General Vinai Thongsong said.

Thai officials over the weekend downplayed the possibility of a successful bomb attack in Bangkok.

"We believe we can take care of it," Prime Minister Yingluck Shinawatra said Sunday.

"The situation is totally under control. The terrorist group has left," Defence Minister General Yuttisak Sasiprapa said.

Despite the high-level assurances, the U.S. embassy in Bangkok had not lifted its travel warning on Monday.

"At this point our warning remains in effect," spokesman Walter Braunohler said. "The emergency measures that were released on Friday are very much still in effect."

Ten other embassies including Australia, Canada, Germany and Israel also issued travel warnings.