Miami ? Three legal immigrants in a cargo truck were detained at the Port of Miami on Sunday after a routine inspection raised concerns, but police say the incident may have stemmed in part from a language barrier.

The port’s cargo area was shut down Sunday as the Miami-Dade bomb squad X-rayed the truck and scanned it for radioactive materials. Nothing unusual was found, officials said.

The men in the truck – two Iraqis and one Lebanese national – were still detained by local police Sunday evening, but authorities said no federal charges were expected. Officials initially said the men, all permanent U.S. residents, had been caught trying to slip past a checkpoint at the port’s entrance.

A port security officer became suspicious when the truck driver could not produce proper paperwork in a routine inspection to enter the port about 8 a.m., Miami-Dade police spokeswoman Nancy Goldberg said.

The driver also indicated he was alone in the truck, though security officers found two other men in the cab, she said. The two passengers, ages 28 and 29, were a friend and a relative of the 20-year-old Iraqi driver, she said.