Travellers were told to expect disruption today after a security alert forced the temporary closure of part of Heathrow Airport.

British Airports Authority said "the majority" of Terminal Two had been evacuated as a precaution because of a suspect package in the check-in area.

Scotland Yard confirmed that officers were dealing with the incident.

Passengers due to travel are urged to contact their airline or visit heathrowairport.com for up-to-date information.

Responding to a report that a man had run up to a desk, dropped off a package and run off, a Metropolitan Police spokeswoman said: "That is certainly a line of inquiry and CCTV is being checked."

But following a report that the desk concerned had been an Air Algeria check-in, she said: "The bag was not found near the Air Algeria desk."

An airport spokesman said Terminal Two later reopened. "After an initial investigation by the police, Terminal Two was reopened at approximately 1700," he said.

"During the time Terminal Two was closed, arriving passengers on Terminal Two airlines were disembarked with their luggage at Terminal One. Some disruption to Terminal Two operations should be expected for the remainder of the day."

Passengers were still experiencing delays in entering the building as staff called travellers through flight-by-flight, prioritising those flights leaving first.

As a result, queues were building at each of the terminal entrances although staff were working to get people through.

Dave Winship, travelling to Zimbabwe on a 7pm flight, said it looks unlikely that he would leave on time. "What annoys me more than anything else is that there is no information," he said.

"They're relying on some poor bloke shouting down the queue. If I'm at the end how am I supposed to know when they are calling my flight?"

A spokeswoman for BAA said: "Re-entry into the building is now being done in a managed way. If we let all these people come in at once, then check-in would just shut down, so we're calling people flight by flight.

"As soon as that process is put in place, then the terminal will become fully operational and flights will begin to leave."