Police evacuated a terminal at Heathrow airport Friday because of a suspect bag, but lifted the alert within 90 minutes in the second major disruption at British airports in two days.

With security at Europe's busiest airport at a high level because of a terrorist threat, police discovered the bag in Terminal 2, which mostly serves European destinations, at around 11:20 a.m. and emptied the building.

Officers checked and cleared the bag and allowed passengers to return about 90 minutes later.

Nine people have been arrested near British airports this week as police and soldiers step up security amid fears of an attack on a plane. Police in northern England said Friday they had arrested two men who were found acting suspiciously near a perimeter fence at Leeds-Bradford airport.

The pair, aged 25 and 26, were arrested Thursday evening under the Terrorism Act and were being questioned by police.

Two men arrested Thursday in Hounslow, near Heathrow, were released without charge Friday, police said. One was handed over to immigration authorities, the other was freed.

Thames Valley Police arrested four other suspects in Langley, five miles northwest of Heathrow, on Thursday afternoon. Police did not say whether the arrests were connected to the terror threat officials say is facing London, or whether any weapons were seized.

Police were also questioning a 37-year-old Venezuelan man arrested Thursday at Gatwick Airport for carrying a suspected live hand grenade in his luggage. He arrived on a flight from Caracas on Thursday afternoon, and his arrest led officers to shut the airport's North Terminal for several hours.

Police have warned that Osama bin Laden's al-Qaida network might try attacking London during this week's Muslim festival of Eid al-Adha. The warning prompted visibly higher security at major airports and in the center of the capital.