Ukrainian President Viktor Yanukovych said Saturday that investigators have not yet determined who was responsible for four explosions in an eastern city and have offered a 2 million hryvna ($250,000) reward for information to solve the case.

The Health Ministry said 30 people, three more than initially reported, were injured Friday when bombs blew up in garbage bins in Dnipropetrovsk. About 20 people remained hospitalized on Saturday.

Many Ukrainian officials have called the blasts terrorist attacks. The opposition has claimed they could be part of a government plot to divert attention from the imprisonment of opposition leader Yulia Tymoshenko.

Interior Ministry investigator Vasyl Farinnik, however, said on Friday that he saw no politics in the attacks, which he said appeared to be of a criminal nature. Ukraine has seen previous explosions connected to criminal extortion.

Top law enforcement officials rushed to Dnipropetrovsk to investigate, and Yanukovych joined them in the city on Saturday. He said the investigators had made some progress in reducing the number of possible scenarios, but he gave no details.