The Meteorological Agency's Sendai office received a number of inquiries Wednesday morning over a white balloon-like object floating in the sky over the city, leaving agency officials bewildered and some Twitter users excited.

"It is not something flown by the meteorological agency, and we don't have a clue what it is," an agency official said. "We checked with the Sendai Municipal Government and the Self-Defense Forces, but they don't know either."

According to the agency, phone calls asking what it is started to arrive at around 7 a.m. A cross-shaped object is hanging underneath the sphere, and it hardly moves. An agency official said it looks like some kind of an observational instrument.

The transport ministry's Sendai Airport office said it has not received any request for approval to fly objects based on the aviation law. "Since it is not on the flight paths of airplanes, it won't affect aircraft operations, but we will continue watching it," an official at the office said.

"Is it a UFO?" one Twitter user said, while another said, "It looks like a hot air balloon."