San Diego ? Investigators believe the San Diego-based Sept. 11 hijackers who helped crash an airliner into the Pentagon initially were sent to California to pinpoint targets in the Navy’s largest West Coast port, a federal law enforcement source told The Associated Press.

Investigators believe al-Qaida operatives Nawaf Alhazmi and Khalid Almihdhar, who arrived in California in January 2000, most likely were assigned to identify San Diego-based Navy ships to attack, said the federal official, who spoke on condition of anonymity.

In October 2000, al-Qaida attacked the Navy warship USS Cole in Yemen.

Alhazmi and Almihdhar were aboard American Airlines Flight 77 when it crashed into the Pentagon, but concern about a plot to target warships in San Diego did not die with them.

In May, the FBI began checking with dive shops in the city and around the country to see if al-Qaida operatives had been taking scuba training. Special operations Navy divers and San Diego Harbor police started training in July to spot potential terrorist threats in the port, and the U.S. Coast Guard has asked recreational boaters to look for and report any suspicious activity.

San Diego is home to two nuclear-powered aircraft carriers and five nuclear-powered submarines, as well as the headquarters of the SEALs, the Navy’s special operations force. A signature feature of the region is the two-mile bridge that links San Diego to Coronado.

The city served as a base for a “high number of hijackers and associates who lived, worked and studied” in the area, James Nagel, a special agent with the State Department’s Bureau of Diplomatic Security, has said in court documents.

John Iannarelli, an FBI spokesman in San Diego, said his agency is investigating the extent of the hijackers’ support network in or near the city. He would provide no further details.

In a recent interview, Gov. Gray Davis said, “the FBI has shared with us the probability of at least a couple cells active in California.”

An al-Qaida training manual recovered by police in England lays out the organization’s missions. Topping the list is gathering information about “the enemy, the land, the installations.” No. 6 is “blasting and destroying the places of amusement, immorality and sin,” and No. 8 is “blasting and destroying bridges leading into and out of the cities.”

Last month, authorities in Spain seized videos of the Golden Gate Bridge, Disneyland and Universal Studios from suspected al-Qaida terrorists.

Investigators in San Diego have divulged little of what they’ve learned about Almihdhar and Alhazmi. The pair attended a local mosque, worked at a gas station and took a few flight lessons. Almihdhar flew home to Saudi Arabia but returned in the summer. By the end of 2000, they were gone.

After the Sept. 11 attacks, authorities questioned anyone who met with them and rounded up a handful of Middle Eastern men as material witnesses, three of whom were charged with crimes unrelated to terrorism.