Houston - A Continental Airlines pilot told air traffic controllers that an object with a flaming tail and a trail of smoke flew in front of the plane shortly after takeoff, FBI officials said.

The FBI's Joint Terrorism Task Force is involved in the investigation, but officials said they believe the object seen by the pilot just east of Houston's airport on Monday was a model rocket.

Officials are unsure how high the object flew or how close it came to the plane, Federal Aviation Administration spokesman Roland Herwig said.

The Boeing 737 carried 148 passengers, authorities said. The plane was never in danger and landed safely, said Scott Wilson, a spokesman for the FBI's Cleveland office.

The FBI routinely looks into any suspicious activity that involves an airplane, bureau spokeswoman Shauna Dunlap said.

"We don't know if it was a rocket or what," she said. "We will interview everyone and determine the validity of what was seen."

Continental Airlines spokeswoman Kelly Cripe would not discuss what crewmembers saw.

Model rockets can reach as high as 40,000 feet, although enthusiasts are supposed to notify the FAA if a rocket is entering controlled airspace, said Robert Morehead of the Amateur Spaceflight Association in Houston.