An intruder who initially identified himself as an Iranian national after being arrested Tuesday for trespassing at a Naval warfare center in Southern Maryland was released yesterday after questioning by federal law enforcement and immigration officials.

Federal officials said they had no records of the trespasser, who reported his name as Moulena Shahabd and his home address as Tehran, and said they had no reason to detain him after questioning.

Shahabd was found within a high security area of the Naval Electronic Systems Engineering Activity near St. Inigoes, one of the Navy's most sensitive electronic warfare centers, about 6 p.m. Tuesday, officials said.

Naval sources at the facility said the arrest had raised new concerns over possible attacks by Iran within the United States as a reaction to the U.S. Navy escorting operations for reflagged Kuwaiti oil tankers in the Persian Gulf.

Navy officials at the facility said yesterday they had not determined how the man had penetrated what is considered a highly secure area.

According to a U.S. Immigration and Naturalization official, Shahabd "did not appear to have all his faculties" and was unable to coherently answer many of the questions posed by investigators.

"The case did not warrant federal prosecution. There were no extenuating circumstances," said Assistant U.S. Attorney Steve Percell.

"All the necessary agencies have completed all the necessary checks and there is no further need to question him," said Donald Crocetti, deputy district director of Immigration and Naturalization Service in Baltimore, adding that immigration officials were "unable to establish that he was illegally in the country."

Although immigration officials said they had no records of Shahabd, they said he was "probably either a lawful resident or a naturalized U.S. citizen."

"He had the appearance of a Middle East or Iranian national, but he had an outstanding command of the American language," leading investigators to believe that he had been in the United States for many years, Crocetti said.

He added, however, that details of the investigation, such as how Shahabd gained entrance to the naval facility were unavailable, but it was reported by law enforcement officials that he was not armed at the time.

Meanwhile, officials at the Naval Air Station at Patuxent said security has been tightened at naval facilities throughout Maryland, Virginia and the District, as a result of the incident.

According to law enforcement officials, Shahabd, who appeared to be in his mid-thirties, had been "cooperative" but had changed his name and identity several times after first saying he was from Tehran.

Shahabd was released to a Salvation Army shelter in Baltimore after questioning, immigration officials said, but he departed from the rehabilitation center yesterday morning, according to several persons staying there.