A fifth man has been arrested during an investigation into a possible terrorism threat to a highway tunnel this week, according to court documents.

Maged Hussein, who owns an east Baltimore convenience store that was raided by federal authorities on Tuesday, was taken in to custody on a handgun charge, the documents showed.

Four other men were detained Tuesday on immigration charges and will be deported, according to Mark Bastan, acting special agent in charge at Immigration and Customs Enforcement (search) here.

One of those men, 30-year-old Mohamed Ahmed Mohamady Ismail, came up in a tip about the purported tunnel plot from a source who is in custody in the Netherlands, Bastan said. The tipster said several men would drive vehicles filled with explosives through a Baltimore-area tunnel.

The three other men picked up at the same time as Ismail were identified as Mohamed Mohamed-Abdelhamed, 38, Suied Mohamad-Ahamad, 25, and Ahmad Al Momani, 58. Al Momani is from Jordan, and the others are from Egypt, Bastan said.

Each had failed to show up for separate deportation proceedings, Bastan said.

"Technically, they were fugitives," he said. "Their deportations are just being acted on."

The Baltimore Harbor Tunnel (search) was closed and the Fort McHenry Tunnel (search) was reduced to one lane of traffic in each direction for nearly two hours Tuesday as the raids occurred.

One federal law enforcement officer, who spoke on condition he not be named, said the closures were needed in case the threat was real and the bombers decided to act.