Belgian prosecutors on Monday released a man they had charged in connection with last week’s deadly Brussels bombings, saying they did not have enough information to justify holding him.

The man, named only as Faycal C, had been accused of taking part in the activities of a terrorist group and actual and attempted terrorist murder after being detained on Thursday. His home had been searched but no weapons or explosives had been found.

“The evidence which led to the arrest of the man named as Faycal C has not been backed up by the ongoing investigation. As a result, the person has been freed by the investigating magistrate,” the prosecutor’s office said.

The announcement was a major blow to an investigation that had netted half a dozen people charged with lesser offences in Belgium and others in the Netherlands, Italy and France, where officials said the same network had planned another attack.

Earlier on Monday, police had issued a new appeal for witnesses, saying they were seeking to identify a man seen in video footage wearing a light jacket, with a hat pulled down over his face and glasses. The suspected suicide bombers walking alongside him were dressed in black with their heads uncovered.

Police say one man left a suitcase containing a bomb at the terminal and fled while two others detonated their bombs.

The death toll from the attack on the airport, and a subsequent bombing of a rush-hour metro train, rose to 35 on Monday, excluding the three men who blew themselves up.

Around 340 people were wounded and 96 were still being treated in hospital, of whom 55 were in intensive care, a health ministry statement said.

Four patients deceased in hospital. Medical teams did all possible. Total victims: 35. Courage to all the families. #BrusselsAttacks — Communicatie (@Maggie_DeBlock) March 28, 2016

A Europe-wide hunt for suspects has revealed links with the network that killed 130 people in Paris last November, as well as foiling a new potential attack on France last week, officials said. But several suspects are reported to be still at large.

Islamic State has claimed responsibility for both the Paris and Brussels attacks. These have exposed weaknesses within intelligence services in Belgium, where some of the Paris attackers lived, as well as insufficient co-operation between security services across Europe.

In Washington, White House spokesman Josh Earnest said the US had urged European officials to do a better job of sharing intelligence after the Paris attacks late last year.

“There has been some progress made with regard to that intelligence sharing, but there is surely more that can and must be done,” Mr Earnest said at a press briefing.

Dutch anti-terrorism police arrested a 32-year-old suspect on Sunday in Rotterdam on France’s request, and Italy on Saturday arrested an Algerian suspected of having forged documents for militants linked to the Brussels and Paris attacks.

Germany has also conducted raids but its Federal Criminal Police Office was among European security agencies still hunting for at least eight mostly French or Belgian suspects on the run in Syria or Europe, Die Welt am Sonntag newspaper said.

The US State Department confirmed four US citizens were among victims of nine different nationalities, including Belgian, in the Brussels attacks.

Belgian health minister Maggie De Block said more of those wounded in the attacks had since died. “Four patients died in hospital. Medical teams did everything possible. Total victims: 35,” she said in a tweet.

Other foreigners killed were British, Chinese, Dutch, French, German, Italian and Swedish.

The airport in Brussels remained closed on Monday and the metro was running a reduced service in the capital, which was largely shuttered for the Easter holiday.

There was no sign of the nationalist protesters who clashed with police on Sunday at the Brussels bourse, where mourners have gathered and placed candles, wreaths and messages for victims.

The State Department has declined to name any of the four US citizens killed, citing respect for their families.

Two of them were identified by relatives as Justin and Stephanie Shults, residents of Belgium originally from Tennessee and Kentucky who were last seen dropping off her mother at the Brussels airport before the explosion in the check-in area.

Reuters