British counter-terrorist police said Thursday they arrested three suspects in the deadly homicide bomb attacks on the London transit system in 2005.

No one has ever been charged in connection with the July 7, 2005, bombings, which were the deadliest attack on London since World War II. The four bombers and 52 commuters died in blasts on three subway trains and a bus.

London's Metropolitan Police said two men, ages 23 and 30, were arrested at Manchester Airport in northwest England as they prepared to board a flight to Pakistan. The third man, 26, was detained at a house in Leeds, a city in northern England where police were searching five houses.

All were arrested on suspicion of committing, preparing or instigating acts of terrorism, and authorities aid they were being taken to a central London police station for questioning.

The houses being searched were all in Beeston, a working-class area of Leeds that was home to three of the 2005 bombers. Officers also were searching an apartment and a business in east London.

The Metropolitan Police said investigators remained "determined to follow the evidence wherever it takes us to identify any other person who may have been involved, in any way, in the terrorist attacks."

At least one other person was detained previously in the case, but he was released.

Magdy el-Nashar, an Egyptian chemist, was taken into custody by Egyptian authorities a week after the 2005 attack after British officials said he was suspected of possibly having links with some of the bombers.

He was let go after three weeks, and Egyptian authorities said he had no involvement in the attack. El-Nashar told reporters then that he casually knew two of the suicide bombers while earning a doctorate in biochemistry at the University of Leeds.