Two Northwest Airlines flights from Tokyo were temporarily held away from passenger terminals Wednesday morning after landing in San Francisco and Seattle on fears someone aboard might be carrying anthrax.

Both planes eventually were cleared without incident, and the 369 passengers on the two flights were allowed to clear customs.

The Federal Aviation Administration ordered Northwest not to let 170 passengers off Flight 28 for about 50 minutes at San Francisco International Airport, according to airport spokesman Ron Wilson.

Officials in Seattle took similar action earlier in the morning, detaining Northwest Flight 8 for two hours before removing two male passengers for questioning and releasing the other 199 passengers and 17 crew members.

"For some reason, the FAA has suspicion that a courier or somebody may have had anthrax transferring on these aircraft," Wilson said.

In Tokyo, about 59 of 170 passengers transferred from the Seattle-bound flight to the San Francisco-bound flight, Wilson said. The two flights were at adjacent gates in Tokyo and left around the same time. Wilson said the Seattle-bound flight originated in Manila.

An FAA spokesman in Washington, D.C., said the agency was checking into the reports, but could not comment further.

Northwest wanted to bring the Boeing 747 to the gate in San Francisco, Wilson said, but "the FAA overruled them." Another San Francisco airport spokesman said the FAA held the San Francisco plane as a precaution until the Seattle flight was cleared.

"The FBI asked us after that plane landed to hold the passengers on board," said Northwest spokesman Bill Mellon. "The FBI now has been satisfied there's not an issue there, so they've allowed us to release the passengers."

Mellon said five FBI, U.S. Customs and Immigration and Naturalization Service agents boarded Flight 8 when it landed as scheduled at Seattle-Tacoma International Airport at 6:10 a.m. PST.

There were no unusual incidents during the flight to Seattle from Tokyo's Narita Airport, Mellon said. U.S. officials asked before the plane landed that it be held away from the terminal, he said.