By Jesús Aguado

MADRID, Jan 17 (Reuters) - The European Central Bank has asked some lenders to detail their exposure to Spain's Grifols and its related entities after the drugmaker was accused last week of manipulating its financial accounts by a short seller, sources said.

Grifols denies Gotham City Research's allegations that it has manipulated its debt and earnings through transactions with a related entity, to the extent that its leverage ratio is almost double what the drugmaker has reported.

The ECB has in recent days contacted several banks to describe their current exposure to Grifols and a network of connected companies, three sources with knowledge of the matter told Reuters.

The Barcelona-based pharmaceutical company has net financial debts of 9.5 billion euros ($10.3 billion), according to company data released in September, of which 1.8 billion euros will mature next year.

The lenders contacted include banks from Spain and other eurozone countries, said one of the sources, speaking on condition of anonymity because they were not authorized to talk to the media.

Supervisors want to get a better idea of the exposure, the source said.

The ECB, which monitors the euro zone's largest banks through the Single Supervisory Mechanism, declined to comment.

Grifols has not disclosed which banks and related entities it owes money to and declined to comment when contacted by Reuters.

Grifols' lenders include Santander , BNP Paribas , Bank of America , BBVA and Caixabank, data compiled by LSEG show.

(Report by Jesús Aguado. Edited in Spanish by Marion Giraldo)