The government has given an "investigative committee" four days to determine responsibility for the devastating explosion in Beirut port on Tuesday, Foreign Minister Charbel Wehbe told French radio Thursday.

Lebanese army bulldozers plowed through wreckage to reopen roads around Beirut's demolished port Thursday, a day after the government pledged to investigate this week's devastating explosion and placed port officials under house arrest.

The blast Tuesday, which appeared to have been caused by an accidental fire that ignited a stockpile of ammonium nitrate at the port, rippled across the Lebanese capital, killing at least 135 people, injuring more than 5,000 and causing widespread destruction.

The huge blast at Beirut port has killed at least 137 people, left dozens missing and at least 5,000 wounded, a Lebanese health ministry spokesperson said Thursday.

The Australian government has pledged an initial 2 million Australian dollars ($1.4 million) to the relief effort in Lebanon following the deadly blast that ripped across the capital Beirut.

The staggering videos from the Lebanese capital are grimly familiar to Tommy Muska thousands of miles away in Texas: a towering blast, a thundering explosion and shock waves demolishing buildings with horrifying speed.

It is what the mayor of West, Texas, lived seven years ago when one of the deadliest fertilizer plant explosions in U.S. history partly leveled his rural town. On Wednesday, Muska also couldn't shake a familiar feeling — that yet again, no lessons will be learned.

As black smoke billowed into the sky, Shiva Karout stepped out of his gym with his colleagues and customers to watch. His gym, Barbell House, sits just across the coastal highway from Beirut's port where a fire raged. They were curious.

Then a first boom shook them, and curiosity turned to fear realizing how close they were. "We got a bit scared, and we all went back in," Karout recounted. Tense moments passed, waiting inside, and one of his customers panicked and ran out. Karout went after him.

US President Donald Trump said Wednesday the deadly Beirut explosion may have been an accident, after raising eyebrows earlier suggesting it was an attack.

Trump said it is still unclear what happened, although Lebanese officials have blamed the massive eruption on a poorly secured stockpile of highly volatile fertilizer ingredient ammonium nitrate.

Lebanon's diaspora, estimated at nearly three times the size of the tiny country's populatio of five million, has stepped up to provide assistance following the massive explosion that laid waste to the capital Beirut.

In Beirut's beloved bar districts, hundreds of young Lebanese ditched beers for brooms on Wednesday to sweep debris in the absence of a state-sponsored cleanup operation following a deadly blast.

Lebanon's flag was projected from Tel Aviv's city hall on Wednesday after the devastating Beirut blasts, in Israel's latest gesture towards a country with which it is technically at war.