The Prime Minister of Lebanon has vowed those responsible for the Beirut explosion will "pay the price".
The enormous blast destroyed the city's port on Tuesday, killing at least 100 people and injuring more than 4,000.
Its cause remains unclear, although authorities have blamed an enormous supply of ammonium nitrate for the explosion that sent a shockwave through the city.
In a televised speech, Prime Minister Hassan Diab implied someone was to blame for the blast at the "dangerous warehouse", adding "those responsible will pay the price".
President Michel Aoun said that 2,750 tonnes of ammonium nitrate, used in fertilisers and bombs, had been stored for six years at the port without safety measures, which he called "unacceptable".
He called for an emergency cabinet meeting on Wednesday.
Officials did not say what caused the blaze that set off the blast. A security source and media said it was started by welding work being carried out on a hole in the warehouse.
"It's like a war zone. I'm speechless," Beirut's mayor, Jamal Itani, told Reuters while inspecting damage on Wednesday that he estimated would cost billions of dollars.
"This is a catastrophe for Beirut and Lebanon."
The head of Lebanon's Red Cross, George Kettani, said at least 100 people had been killed.
"We are still sweeping the area. There could still be victims. I hope not," he said.
Kettani earlier told broadcaster LBCI that the Red Cross was coordinating with the health ministry to set up morgues because hospitals were overwhelmed.
Hours after the blast, which went off shortly after 6pm (1500 GMT), a fire blazed in the port district, casting an orange glow across the night sky as helicopters hovered and ambulance sirens sounded across the capital.
The blast was heard throughout Cyprus, which is about 100 miles (160 km) away.
It revived memories of a 1975-90 civil war and its aftermath, when Lebanese endured heavy shelling, car bombings and Israeli air raids.
Some residents thought an earthquake had struck. Dazed, weeping and injured people walked through streets searching for relatives.
"The blast blew me metres away. I was in a daze and was all covered in blood. It brought back the vision of another explosion I witnessed against the U.S. embassy in 1983," said Huda Baroudi, a Beirut designer.
Rodney Eid, assistant director for crisis management at Red Cross Lebanon, says he expects the death toll to rise.
"The preliminary report indicates around 4,000 people have been injured and at least 100 have lost their lives," he told BBC Radio 4's Today programme.
"Our teams are still searching the area, and it is a big area, around the blast - to look for survivors, to look for people who are injured.
"We have also set up two triage and first aid locations next to the blast area so that minor injuries can be treated there as we were overwhelmed with the number of calls yesterday and we were trying to respond to the most vulnerable and to the critical cases first."
Mr Eid said "there are a lot of people who are missing", and added: "I expect the death toll to rise."