Three of the four people arrested last month in connection with an investigation into the nerve gas sarin were released from jail by a court in Maastricht on Monday. The fourth suspect was released last week.

The court said there is not enough evidence to keep the three in custody and the public prosecution department will not appeal against the decision, Nos television reported. Nevertheless, the department says the four are still considered suspects.

Police spent an entire weekend searching woods near Maastricht for the gas after a tip-off that sarin was being offered for sale. Despite an intensive search, involving helicopters and cutting down trees, no traces of the nerve gas were found.

Lawyers Arthur Vonken and Theo Bouwmans said on Monday the public prosecution department had no case, stating that the person who tipped off police had heard several years ago that sarin had been buried in Amby, near Maastricht.

An undercover police officer then put pressure on the main suspect, a 35-year-old man, to dig in the woods, where he and a 53-year-old woman were arrested, Vonken said.

Bouwmens said his 21-year-old client had been mentioned in telephone taps but played no further part in the case.