UPDATE 1-Girl dies after receiving cervical cancer vaccine

* Glaxo says cause of death unknown

* Batch of vaccine involved quarantined

* FDA approval decision expected soon (Adds U.S. approval decision expected, competition)

LONDON, Sept 28 (Reuters) - A teenage British girl died after receiving a cervical cancer vaccine made by GlaxoSmithKline (GSK.L), but a link between the death and the drug has not yet been established, health officials said on Monday.

The 14-year-old fell ill after she was given the Cervarix vaccination against the sexually transmitted human papillomavirus (HPV) at her school in Coventry, central England, as part of a national immunization program. She later died in a hospital.

"The incident happened shortly after the girl had received her HPV vaccine in the school," Dr. Caron Grainger, joint director for Public Health for NHS (National Health Service) Coventry and Coventry City Council, said in a statement.

"No link can be made between the death and the vaccine until all the facts are known and a post mortem takes place," Grainger said. "We are conducting an urgent and full investigation into the events surrounding this tragedy."

Glaxo said it was working with the Department of Health and MHRA (Medicines and Healthcare products Regulatory Agency) to better understand the case.

"At this stage the exact cause of this tragic death is unknown," Glaxo medical director Dr. Pim Kon said in a statement.

"As a precautionary measure, the batch of vaccine involved has been quarantined until the situation is fully understood," Kon added.

News of the death comes on the eve of a possible decision by U.S. health regulators on whether to approve Cervarix for sale in the United States. However, the U.S. Food and Drug Administration often lets its expected action dates pass without a decision, or announces a delay.

A small number of other girls at the school reported mild symptoms such as dizziness and nausea but were not admitted to a hospital, health officials said.

GlaxoSmithKline, based in Brentford, Middlesex, said more than 1.4 million doses of Cervarix had been given as part of the national immunization program.

It said adverse reactions reported so far had related to signs and symptoms of recognized side effects, or were due to the injection and not the vaccine itself.

Cervarix is administered in three separate shots over six months.

Should it gain U.S. approval it would compete with Merck & Co's (MRK.N) Gardasil, which has been in the market in the United States since 2006 and had sales of $268 million in the second quarter. (Reporting by Michael Holden; additional reporting by Bill Berkrot in New York; Editing by Michael Roddy, Bernard Orr)