Seoul, South Korea (CNN) -- Investigators believe a single person is responsible for planting two small bombs at Seoul's main railway station and bus terminal, South Korean officials said Friday.
The bombs, which were planted in coin lockers, went off within an hour of each other late Thursday morning, according to a written statement released by the Seoul Metropolitan Police Agency.
There were no injuries reported in the explosions that police said they now believe "appears to be the work of a single suspect," the statement said.
Police said Friday they were searching for a man spotted on surveillance video placing a backpack in one of the lockers at Seoul's train station hours before the explosion.
Merchants at the train station first alerted authorities to a possible explosion after they saw smoke coming out of one of the lockers, police said.
Less than an hour later, police said they received a report of another explosion in a locker at the bus terminal.
The two devices, which were almost identical, were made using a gas canister, a digital timer and batteries, police said.