As of early Tuesday there was no claim of responsibility. Prayuth Chan-ocha, the head of Thailand’s military government, said that the authorities were searching for a person seen on closed-circuit footage but that it was not clear who the person was, news agencies reported.

A spokesman for the police, Lt. Gen. Prawut Thavornsiri, told a Thai television interviewer that “we haven’t concluded anything.” The authorities said they were reviewing footage from 15 security cameras in the area but that the rush-hour crowds made deciphering the video difficult.

“The shrine was very crowded,” General Prawut said. “It’s not clear even looking at the CCTV footage.”

The bomb, General Prawut said, was placed under a bench on the outer rim of the shrine’s grounds. Initially, the police said they had discovered at least two additional devices that they suspected were unexploded bombs inside the shrine and said other bombs may have been placed in the area, yelling at bystanders: “Get out! Get out!”