The state-run National News Agency (NNA) quoted Judge Fadi Akiki, a government representative at Lebanon's military court, as saying authorities had so far questioned more than 18 port and customs officials and individuals responsible for or involved in maintenance work at the warehouse housing highly explosive material that blew up.
"Sixteen people have been taken into custody as part of the investigation," NNA quoted Akiki as stating, without naming the individuals.
He added that the investigation was continuing.
After the explosion rocked the capital city of Beirut on Tuesday, the Lebanese government has decided to put all officials who oversaw storage and security there since 2014 under house arrest, until investigations are complete.
Lebanon's central bank has also ordered a freeze on the accounts of the heads of Beirut port and Lebanese customs along with five others, according to a central bank directive seen by Reuters news agency and confirmed by the central bank.
The investigation is being conducted by a special committee headed by the Justice Minister and includes Prime Minister Hassan Diab and the heads of major security agencies.
The government of Lebanon has given the "investigative committee" four days to determine responsibility for the devastating explosion in Beirut port, Foreign Minister Charbel Wehbe told French radio on Thursday.
Lebanese rescue workers and army soldiers are struggling to remove huge items of debris in search for possible survivors at Beirut's port.
The Lebanese Red Cross believes there are still 100 people missing, most of who were working at Beirut's port.
"We are doing our best as we are hoping to find people alive and trapped, but all we have found so far are the remains of people beyond recognition," said a rescue worker, who stated he has been working non-stop for the past 48 hours.
"Some foreign countries are sending help, but it might be too late for the people who may still be trapped under the debris," he added.
Lebanon's Ministry of Health announced that 157 people have been killed in the blast at Beirut's port on Tuesday, while at least 5,000 others have been injured. The explosion left 300,000 homeless, as vast part of the city has been fallen into ruin.
Red Cross volunteers at the scene of the explosion declared they expect the death toll to rise.
Terrifying footage showed a huge mushroom cloud of fire and smoke covering much of Beirut’s port area, blowing out windows and destroying buildings in the neighborhood, as a warehouse at the Beirut docks caught fire on Tuesday afternoon.
Photos on social media showed many buildings in the area damaged or destroyed, leaving residents covered in glass and blood.
Several smaller explosions were heard before the bigger one occurred and turned the city’s streets into a debris-strewn wasteland.
Health Minister Hamad Hassan blamed the explosion on a fireworks accident, ordering all hospitals in Beirut to prepare for the victims of the incident.
Head of the Lebanese Red Cross George Kettaneh also stated that hundreds of injured people were taken to hospital for treatment, while some still remain trapped in their homes.
The Health Ministry announced all Beirut hospitals are overcrowded with those injured in the incident and can no more accommodate anyone.
Yet, the Health Minister told Lebanon's LBC News that hundreds are feared dead and thousands have been wounded in the blast. He added that the death toll now stands at over 157.
The Lebanese Red Cross also declared that over 5,000 people have been wounded in the incident, while the numbers are still expected to rise. It added that over 157 dead bodies have been collected from the scene of the incident so far.
Beirut Governor Marwan Abboud called it a "national catastrophe" and the prime minister declared a day of mourning.
“It resembles to what happened in Japan, in Hiroshima and Nagasaki. That’s what [it] reminds me of. In my life, I haven’t seen destruction on this scale," Abboud added.
Badri Zaher, Director General of the Lebanese Customs House, declared that dozens of tons of nitrate had exploded in the port of Beirut.
Lebanese General Security Director Abbas Ibrahim also dismissed rumors of Israeli involvement, noting that a large cache of highly explosive sodium nitrate was stored at the site, after being confiscated off a ship several months ago. But he did not explain how the fire has started.
Early reports claimed a short-circuit has likely sparked fire at the warehouse where the huge sodium nitrate cargo was kept and fire later spread to an adjacent warehouse where a huge cargo of fireworks was stored.
Yet, there is still no official report on the exact cause of the blast, a UN spokesperson told reporters that his organization is still unsure whether the explosion was "an accidental or man-made act".
The Israeli Defense Force has denied responsibility for the massive explosions in Beirut. Hezbollah has also denied the blasts were the result of a rocket attack.