BANGKOK – A police manhunt was underway Wednesday for an “unidentified foreign man” shown in a security video leaving a backpack at a popular Bangkok shrine just minutes before a bomb exploded there.

Two other people seen on the video near the man are also considered suspects in Monday’s deadly bombing, police said.

Authorities released a sketch of the man who left behind the backpack and offered a $28,000 reward for information leading to his arrest. But apart from the rough portrait, they had few solid leads in Monday’s bombing at the Erawan Shrine that killed 20 people and wounded 120 others.

The grainy security video shows the man, wearing a yellow T-shirt and shorts, sitting down on a bench at the shrine, taking off a black backpack and leaving it behind as he stands up and walks away. Time stamps show he left the shrine 15 minutes before the explosion, which struck just before 7 p.m.

The two possible accomplices are seen standing in front of the man, police spokesman Lt. Gen. Prawut Thavornsiri said. One of the men is wearing a red shirt and the other is in white, and they are seen leaving the area shortly before the man in yellow also leaves.

At a news conference, Prawut expressed uncertainty about the man’s origin, saying the suspect “looks like a foreigner” but “might have been in a disguise and wearing a fake nose” to conceal his identity.

Prawut told reporters Wednesday night that police would continue to scrutinize closed-circuit TV footage of the area from before the blast for clues about suspects. He said that if the men in red and white shirts were innocent and aware of the suspicions against them, they should report to police.

Two days after the attack, which authorities have called the worst in Thai history, the shrine reopened to the public. No one has claimed responsibility for the blast at one of the capital’s busiest intersections during evening rush hour.

“If citizens or anyone can give us information or clues that lead to the arrest of this man, I have set a reward of 1 million baht,” National Police Chief Somyot Poompanmoung said.

“He didn’t do it alone, for sure. It’s a network,” he said.

Police composed the sketch based on the video and a description provided by a motorcycle taxi driver believed to have given him a ride on Monday night.

The sketch shows a young man in eyeglasses with bushy, dark hair. The warrant describes him as tall, with a pointed nose and thick lips. He faces six charges including conspiring to commit premeditated murder and conspiring to commit a bombing that resulted in death and severe injuries.

The attack has raised concerns about safety in a city that draws millions of tourists.

Prime Minister Prayuth Chan-ocha “is worried about the security of people and tourists in Thailand,” the police chief said.

Thai authorities identified six victims as Thai and four as Malaysians, along with four Chinese, two people from Hong Kong including a British citizen, one Indonesian and one Singaporean. Two victims remain unidentified.

A funeral was held Wednesday for 45-year-old Waraporn Changtam, one of the victims of the bombing.

“I don’t know who you are mad at, but don’t take it out on my family,” said Sawaros Kumrit, her older sister, adding that those killed by the bomb “were good people. They were innocent.”