BERLIN — Google came under increased pressure in Europe on Tuesday over its collection of private data from unsecured home wireless networks as a German regulator threatened legal action if the company did not surrender a hard drive for inspection.

The German demand underscored the seriousness of the quandary Google now faced after its admission last Friday that it had stored the snippets of Web sites and personal e-mail messages from people around the world while compiling its Street View photo archive.

Johannes Caspar, the data protection supervisor for the city-state of Hamburg, where Google’s German headquarters are located, said Tuesday that he had given Google until May 26 to hand over one of the hard drives that it had used to collect and store information in Germany, where Street View is not yet available.

Through a spokesman, Google reiterated its offer to destroy the WLAN data in conjunction with regulators, but stopped short of saying it would hand over a hard drive, which would allow regulators to see for the first time what kind of data had been collected.