Bombs used by four suicide attackers to kill 52 people in London were made from simple ingredients such as hair bleach, and three of them were probably set off by cellphones, New York?s police chief said. The homemade devices used on July 7 were stored in a commercial refrigerator in an apartment in northern England and shipped in coolers to a station outside London where the bombers took a train to the capital, Raymond Kelly said.

?Initially it was thought that perhaps the materials were high-end military explosives that were smuggled, but it turns out not to be the case,? Kelly told a briefing of security chiefs from large New York companies on Wednesday, according to US media reports.

?It?s more like these terrorists went to a hardware store or some beauty supply store.? The briefing, partly based on information obtained by New York officers sent to London to monitor the police inquiry, provides the first detailed account of the explosives and methods used by the London bombers on July 7.

British police say four British Muslims killed themselves and 52 other people with bombs on three underground trains and a bus. Exactly two weeks later, police say, four men failed in a similar attempt when their bombs did not detonate. Britain?s anti-terrorist branch would not confirm the US reports and have previously said details about the explosives could be an important part of their probe. Officers indicated they were unhappy with the US revelations.