It is only a breathless Hollywood script: treasure-hunter Indiana Jones races with German archaeologists to track down the fabled Ark of the Covenant, the chest that held the stone tablets on which the Ten Commandments were etched.

Now German researchers claim to have found the remains of the palace of the Queen of Sheba - and an altar that may have held the Ark.

The discovery, announced by the University of Hamburg, has stirred sceptical rumblings from the archaelogical community. The location of the Ark, indeed its existence, has been a source of controversy for centuries.

Regarded as the most precious treasure of ancient Judaism, it is at the heart of a debate about whether archaeology should chronicle the rise and fall of civilisations or explore the boundaries between myth and ancient history.

Professor Helmut Ziegert, of the archaeological institute at the university, has been supervising a dig in Aksum, northern Ethiopia, since 1999.

"From the dating, its position and the details that we have found, I am sure that this is the palace," he said. The palace, that is, of the Queen of Sheba, who is believed to have lived in the 10th century BC.

After she died her son and successor, Menelek, replaced the palace with a temple dedicated to Sirius. The German researchers believe that the Ark was taken from Jerusalem by the Queen - who had a liaison with King Solomon - and built into the altar to Sirius.

"The results we have suggest that a Cult of Sothis developed in Ethiopia with the arrival of Judaism and the Ark of the Covenant, and continued until 600AD," an announcement by the University of Hamburg on behalf of the research team said. Sothis is the ancient Greek name for the star Sirius.

The Ark was made, according to the Bible, of gold-plated acacia wood and topped with two golden angels. It is said to be the source of great power. In about 586BC, when the Babylonians conquered the Israelites, the Ark vanished.

For many centuries finding it has been one of the great quests - inspiration not only for the 1981 film Raiders of the Lost Ark, but also for countries seeking to position themselves in the mainstream of ancient civilisation.

Many archaeologists believe that their profession should not be in the business of myth-chasing. Even if the Ark were found it would be impossible to establish scientifically whether it was the original receptacle for the Ten Commandments.

Iris Gerlach, of the German Archaeological Institute in Sanaa, Yemen, believes the religious centre of Sheba is in present-day Yemen.

Although she does not go headto-head with her colleague Professor Ziegert, the message is clear: a relic such as the Ark would have been stored in an important relgious city rather than Aksum.

Quest goes on

- The location of the Ark has been put in Egypt, Zimbabwe and even Ireland, where the Hill of Tara was excavated.

- The Ethiopian holy town of Aksum is regarded as a more credible site.

- Ethiopians believe that it is defended by monks in the church of St Mary of Zion and is seen only by the guardian of the Ark, making it impossible to verify.