BEIRUT (Reuters) - A large fire erupted at Beirut port on Thursday, engulfing parts of the Lebanese capital in a pall of smoke weeks after a massive blast devastated the port and surrounding residential area.

The blaze began in the shattered duty free zone of the port, prompting some residents to flee the city still traumatised by last month’s explosion which followed a port fire.

Army helicopters dropped water as firefighters battled on the ground to bring the blaze under control. By evening, officials said most flames had been extinguished. Smoke still rose from smouldering wreckage but it was far less dense.

“For sure we were scared, it’s only been a month since the explosion that destroyed Beirut. We saw the same thing happening again,” 53-year-old Andre Muarbes said as soot and ash fell on vehicles and buildings across parts of the capital.

Officials said no one had been injured, but the blaze strained nerves already on edge in a nation grappling with a deep economic crisis that has posed the biggest threat to Lebanon’s stability since its 1975-1990 civil war.

Michel Najjar, public works minister in the outgoing government which resigned in the wake of the blast, told Lebanon’s MTV initial indications suggested the blaze was sparked by welding work during repairs at the port.

A military source said it appeared to have started when cooking oil caught fire and spread to stores of tyres. At one point, live television footage had shown flames licking up near a pile of tires in a warehouse ruined by last month’s explosion.

The Aug. 4 blast killed about 190 people and injured 6,000.

Majed Hassanein, 49, was taking his wife and two children out of the capital by car during the height of the blaze. “I am forced to get them out of Beirut from the smoke and the fire that is happening at the port again,” he said.

His son, he said, was still suffering shock from the blast that ruined a swathe of capital near the port, leaving about 300,000 people without inhabitable homes and shattering windows across the city.

The head of Lebanon’s Red Cross, George Kettaneh, said there were no injuries but some people suffered shortness of breath.

The public prosecutor ordered an immediate investigation. Many Lebanese are frustrated that they have not been told about any initial findings from an investigation into the port blast, more than a month after it ripped through Beirut.

Carmen Geha, an activist and associate professor at the American University of Beirut, said the fire was further proof of mismanagement by a ruling elite, who have dragged the nation into crisis after years of corruption and poor governance.

“It’s a gross crime, gross negligence and gross arrogance,” she said. “You can’t trust them to manage anything.”

Firefighters were shown in television footage dousing the port fire surrounded by mangled remains of warehouses destroyed in last month’s explosion, which was caused by a store of ammonium nitrate that had been kept in poor condition at the port for years.