BRUSSELS, May 3 (Reuters) - The European Commission has warned three Chinese electric vehicle makers that they have not supplied sufficient information for its anti-subsidy investigation, according to two people familiar with the case.

If the Commission concludes that the provided information from sampled companies BYD, SAIC and Geely is insufficient, it could use evidence available elsewhere to compute tariffs, a move that can inflate them.

Warnings of this kind occur frequently in EU trade defence cases. Indeed, for all 10 past anti-subsidy cases against China for which measures are still in place, the Commission used such "facts available" to fill in certain gaps.

The companies have been given the right to respond to the warning, the people said.

BYD, SAIC and Geely did not immediately respond to requests for comment late on a public holiday.

The Commission, which oversees trade policy in the 27-nation European Union, launched an investigation in October into whether battery electric vehicles manufactured in China were receiving distortive subsidies and warranted extra tariffs.

The China Chamber of Commerce for Import and Export of Machinery and Electronic Products (CCCME) said earlier this month that the investigation was stacked against Chinese manufacturers.

Among its complaints was the vast amount of information the Commission has demanded from the sampled Chinese producers.

"It cannot be precluded that the Commission may resort to what is called 'facts available' in trade defence parlance in order to inflate the subsidy margins," CCCME vice president Shi Yonghong said then.

The investigation, officially launched on Oct. 4, can last up to 13 months. The Commission can impose provisional anti-subsidy duties nine months after the start of the probe. (Reporting by Philip Blenkinsop; Editing by Kirsten Donovan)