BERLIN (AP) — A German research organization is searching, so far in vain, for an underwater environmental monitoring station that was moored on the sea bed and went missing last month.

The device, which measured water flow and methane concentration among other things, was located 22 meters (72 feet) under the surface of Eckernfoerde Bay in northern Germany. It weighed some 740 kilograms (1,630 pounds) and was moored by thick cables.

The Geomar ocean research center says data transmission ended abruptly Aug. 21. Researchers first suspected a transmission failure, but divers sent down last week discovered that the equipment was missing and saw only a frayed cable.

News agency dpa reported Thursday that Geomar said divers took a second look this week and found only parts of the station's supports. Police are investigating.