London ? A district judge granted a request by British investigators to keep 23 suspects arrested in an alleged plot to blow up trans-Atlantic jetliners in custody for another week without filing charges.

It was the first major test of a new terrorism law that allows suspects to be held for as long as 28 days without charge so investigators can solidify their cases.

A person arrested on Tuesday as part of Scotland Yard’s investigation into the foiled plot was released without charge. Another detainee was released without charge Friday.