Update as of 6 a.m. EDT: Thai authorities have increased the reward for information about the main suspect in Monday’s Erawan Shrine blast in Bangkok to 3 million baht ($85,000), NBC News reported Friday.

The Bangkok bombing killed at least 20 people and left over 120 injured. On Thursday, Thailand had doubled the reward for information to 2 million baht ($56,000). A Thai businessman on Thursday added 1 million baht to the reward set by police Wednesday.

Original story:

Police in Thailand are searching for a “woman wearing a black shirt” in connection with Bangkok’s Erawan Shrine blast Monday that killed at least 21 people and wounded over 120, a senior official said Thursday. The announcement comes a day after police said that at least 10 people were involved in carrying out the Bangkok bombing.

"I would urge her to come forward to provide information to police," police spokesman Lt. Gen. Prawut Thavornsiri said, without elaborating, according to CNN.

Thailand also doubled the reward for information about the main suspect of the blast to 2 million baht ($56,000), Somyot Poompanmoung, national police chief, said Thursday, according to the Associated Press (AP). He added that a Thai businessman who wanted to remain anonymous had added to the 1 million baht reward set by police Wednesday. Police believe that the main suspect behind the attack is a man wearing a yellow T-shirt and carrying a backpack seen in surveillance footage.

Two men in red and white clothes captured on CCTV footage, who investigators claimed were also suspects, turned themselves in to police Wednesday. The men, however, said they were tour guides and were not connected to the Erawan Shrine bombing. On Friday, police also interrogated an auto-rickshaw driver, who said he drove the main suspect connected to the Bangkok bombing, according to state-run National News Bureau of Thailand.

Thavornsiri reportedly said that the driver picked up the suspect from an unspecified location to Ratchaprasong Intersection near the Erawan Shrine. The driver also told the police that the suspect was a foreigner and communicated through images from a mobile phone and hand gestures. However, the driver could not identify the language the suspect spoke, Thavornsiri said.

Following the deadly blast, Thai police have beefed up security across popular tourist attractions in the country, military spokesman Col. Winthai Suvaree said Friday, according to the AP. He added that Thai security agencies examined the Erawan Shrine, and also increased the number and frequency of security patrols in uniforms and plainclothes. 

Channel News Asia tweeted Friday, citing Thai army spokesman, that people spreading rumors online and causing panic will be prosecuted. The spokesman also requested public to give police time to investigate.

Suvaree also downplayed the theory that the bombing was connected to international terrorism. "Security agencies have collaborated with intelligence agencies from allied countries and have come to the same preliminary conclusion that the incident is unlikely to be linked to international terrorism," he reportedly said.

The Hindu shrine, located in Pathum Wan district, was built in 1956 and is a popular tourist attraction.