A University of Tokyo cosmological institute said Monday that its research data became publicly accessible for some time until Jan. 27 following unauthorized access to its computer server.

The research activities at the Kavli Institute for the Physics and Mathematics of the Universe were interrupted by the unauthorized access, although no major problems, such as data falsification, have been reported.

Observation results from the Subaru Telescope in Hawaii and data from the latest theoretical studies were on the server, according to the institute.

"We feel sorry about causing trouble to other research institutions that are conducting joint studies with us," said Hitoshi Murayama, director of the institute. "We would like to resume our research activities after identifying how it (the intrusion) occurred."

The server in question was disconnected from the network on Jan. 27 after a person operating it detected the unauthorized access.