Cameron said that authorities had immediately banned packages coming to (or through) the UK from Yemen and would be "looking extremely carefully at any further steps we have to take". UK Home Secretary Theresa May said that the government did not believe that the plotters would have known the location of the device when it was planned to explode. Although details of the device found in Britain were not released, photographs emerged in the US media of an ink-toner cartridge covered in white powder and connected to a circuit board. The British government's statements suggested that authorities in the UK and the US remained uncertain about the targets and purpose of the apparent plot. According to Dubai police, the explosives they found were also inside a printer-ink cartridge in a cardboard box with English-language books and souvenirs. The cartridge contained PETN and plastic explosives mixed with lead azide (an explosive commonly used in detonators). Unnamed US officials quoted by the Associated Press said that al-Qaeda's explosives expert in Yemen, Ibrahim Hassan al-Asiri, was the likely suspect in the bomb-making. They said that Asiri helped to make the bomb used in the failed Detroit Christmas Day bomb attack and another PETN device used in a failed suicide attack against a top Saudi counter-terrorism official. The White House said that Saudi Arabia provided information which helped identify the threat, and the UK's "Daily Telegraph" reported that an MI6 officer responsible for Yemen had been tipped off.