Washington, Dec 28 (IANS) Two days after an Amsterdam-Detroit flight was targeted in what prosecutors called a failed attempt to blow up a jetliner, a security alert was sounded on the same Northwest Airlines flight.

The alert ended after investigators determined the new incident Sunday on Northwest Flight 253 -- same as the one on which a Nigerian man is accused of attempting to set off an explosive device Friday - was "non-serious," federal authorities said.

The crew reported a "verbally disruptive" passenger Sunday and requested police to meet the plane when it arrived from the Netherlands, the airline told CNN. The man was questioned by police after the plane landed in Detroit early Sunday afternoon.

Sandra Berchtold, a spokeswoman for the Joint Terrorism Task Force in Detroit, said Sunday's alert was caused by a passenger who "spent a lengthy time in the restroom."

"This raised concerns, so an alert was raised," she said. "JTTF investigated, and the investigation shows that this was a non-serious incident and all is clear at this point."

The passenger spent about an hour in the bathroom and got upset when he was questioned by the crew of the flight from Amsterdam, according to government sources cited by CNN. Law enforcement agents questioned the man Sunday.

Scott Wintner, a spokesman for the Wayne County Airport Authority told CNN the flight "requested emergency assistance and was pulled aside upon arrival in Detroit."

The jet was taken a long distance from the terminal and "completely engulfed" by emergency vehicles and heavily armed police once it landed, said Don Graham, who was waiting for relatives to arrive at the airport.

The flight arrived about 12:34 p.m., said Susan Elliott, a spokeswoman for Delta Air Lines, which owns Northwest. The 257 passengers were allowed to leave the aircraft about an hour after the jet landed, she said.

President Barack Obama vacationing in Hawai was also notified of the new flight scare, White House said.