A government-appointed commission began an inquiry today into the activities of John Allen Muhammad and John Lee Malvo, focusing on allegations of immigration fraud and the nature of the relationship between the two suspects charged in the sniper attacks.

The commission also plans to look into whether Muhammad had been involved with weapons or weapons training on the island, authorities said. Central to the investigation will be allegations that Muhammad forged documents and helped Jamaican nationals enter the United States illegally.

The four-member panel is expected to produce a preliminary report by Thursday afternoon, an indication of how seriously officials here view a possible connection between their island and the suspects in the sniper attacks.

"We want to know whether there is a relationship with the crimes in the United States," Gertel Thom, attorney general for Antigua and the nearby island of Barbuda, said in an interview.

Thom said the government is working closely with the United States on the investigation, noting that two FBI agents are on the island.

Authorities believe Muhammad, 41, first turned up on this small Caribbean island 300 miles east of Puerto Rico in March 2000. He was accompanied by his three children, who then became the subject of a custody dispute with his second wife.

Today, commission members met with the Antigua passport office and determined that Muhammad had obtained only one passport. They were examining allegations, widely believed by government officials here, that Muhammad used the name of a woman from Antigua and passed her off as his mother, enabling him to claim citizenship.

The investigation will also try to determine when Malvo and his mother, Una James, arrived on the island, how the now 17-year-old came to befriend Muhammad and how the two ended up living together, officials said. Among the things they are trying to determine is whether James, a native of Jamaica, entered the island using a different name.

Also a mystery is how Muhammad paid for repeated trips between the island and the United States in 2000 and 2001. Authorities here said Muhammad had only sporadic employment, as a mechanic and painter, which would not have provided him with enough money to support his lifestyle.

"From these odd jobs, it could not have been possible for him to travel to the United States," said Thom. "We need to know where the other sources of income came from."

One way investigators believe Muhammad made money was by forging documents and selling them to foreigners who would then illegally enter the United States. That suspicion is based in part on an incident in March 2001, when Muhammad turned up at the American Airlines ticket counter at an airport here and attempted to check in for a flight to Miami.

Thom said Muhammad submitted a fraudulent birth certificate from Florida and a bogus driver's license from Tacoma, Wash., with his picture. The two documents were in the name of Dwight Russell, Thom said.

An American Airlines ticket agent was suspicious of the documents and alerted authorities. Muhammad was taken to a local police station for questioning but managed to escape, Thom said.

The episode is a window into how the forgery business may have worked. Thom said Antiguan officials believe that a Jamaican named Steve Kelly was to have boarded the flight to Miami. Under the scenario, Muhammad would have checked in at the counter and then given the boarding pass and other documentation to Kelly.

The four-member panel includes two local lawyers, a retired police official and a Catholic priest. Cosmos Marcelle, the police official, said it was "too early to tell" what would emerge from the inquiry. "We just started work this morning," he said.

Sheridan reported from Washington.