Factbox: Shell oil heist: the story so far

By John Geddie and Fathin Ungku

SINGAPORE (Reuters) - Singapore authorities say they have uncovered a complex, cross-border scheme to steal large quantities of oil from Shell's biggest refinery.

Their investigations have so far entangled several international companies in incidents going back months. Fourteen men face charges, the latest of which were announced on Tuesday.

Police have also seized an oil tanker and millions of dollars in cash, and frozen suspects' bank accounts.

And there could be more arrests. Shell first contacted the authorities in August 2017 about suspected theft at its Pulau Bukom site, just south of the country's main island.

Here's what we know so far:

WHO'S INVOLVED?

Among the 14 charged, there are 11 Singaporeans and three Vietnamese.

Eight of the Singaporeans were employees of Shell Eastern Petroleum (Pte) Ltd, the Singapore subsidiary of Royal Dutch Shell Plc, while two others worked for Sentek Marine & Trading Pte, one of Singapore's biggest marine fuel suppliers.

Sentek Marine said the suspects were its marketing and operations manager and a cargo officer. The cargo officer is accused in court documents of receiving stolen goods on a Singapore-owned and -flagged ship, Sentek 26.

The other Singaporean worked for Intertek, a British-listed company specializing in quality and quantity assurance, including for fuel products.

The Vietnamese nationals were charged with receiving stolen property aboard two other ships - Prime South and MT Gaea - both of which are Panama flagged.

Authorities have arrested at least 17 people in connection with the case.

WHAT WAS STOLEN AND WHEN?

The court documents list thefts on several dates over three hand a half months, many of which happened during the refinery's normal working hours and involved millions of dollars' worth of gasoil.

Below is a list of the dates of the incidents and the amount and value of gasoil reportedly stolen.

* Oct. 2, 1,131 metric tonnes of gasoil valued at S$579,445

* Oct. 23, 1,276 metric tonnes (S$653,733)

* Nov. 11, 300 metric tonnes (S$165,000)

* Nov. 14, 846 metric tonnes (S$465,520)

* Nov. 21, 2,322 metric tonnes (S$1,277,430)

* Dec. 31, 1,076 metric tonnes (S$592,295)

* Dec. 31, 1,348.8 metric tonnes (S$736,444.80)

* Jan. 5, 801.86 metric tonnes (S$437,815.56)

* Jan. 7, 1,260 metric tonnes (S$687,960)

WHERE WAS THE OIL HEADED?

There have been three ships named in court documents as having received the stolen oil - Prime South, Sentek 26 and MT Gaea.

Over the last three months, those vessels have travelled between ports in Singapore, Vietnam, Thailand and Indonesia, shipping data from Thomson Reuters Eikon show.

WHAT'S NEXT?

Singapore police say investigations are still ongoing. Six of 17 men initially arrested have yet to face charges.

Some of those charged so far are due back in court on Jan. 18 and Jan. 22, and may face additional charges.

(Compiled by John Geddie and Fathin Ungku)