More gold and silver, including a gold and garnet cross, an eagle-shaped mount, and what could be a helmet cheek piece, have been churned up by ploughing in Staffordshire in the same field which three years ago yielded one of the most spectacular Anglo Saxon hauls.

When archaeologists first scoured farmer Fred Johnson’s field in Hammerwich and discovered the hoard, which comprised more than 3,500 fragments of metalwork including sword, shield and helmet mounts inlaid with pieces of garnet and enamel, they left convinced they had emptied it of every scrap of treasure. Now a 90 further pieces have been found.

The workmanship in the new finds appears identical to pieces from the original haul; the helmet cheek piece appears to match one found three years ago.

Experts from English Heritage and Staffordshire county council, who were confident they had uncovered the field’s secrets when the hoard was found by amateur metal detectorist Terry Herbert, believe the latest finds must be connected, but a formal decision on that will be taken by the local coroner, Andrew Haigh, in a treasure inquest next month.

If the finds are indeed linked, it will be particularly valuable to the archaeologists because no evidence was found of how such a hoard – 5 kg of gold and 1.5 kg of silver, described at the time as the equivalent of finding a new Lindisfarne gospels or Sutton Hoo treasure – came to be in the field: there was no grave, hut or trackway, though it is close to the Watling Street Roman road.

It has been suggested the items form part of a war booty, found in the heartland of the Mercians, and either awarded to the winners or looted from the losers of some long-forgotten battle. Apart from the enigmatic crosses, almost all the pieces are warrior swagger. Most are twisted as if wrenched from their original mounts – including the crosses, one of which bears the wonky Latin inscription: “Rise up, O Lord, and may thy enemies be dispersed and those who hate the be driven from thy face”.

The latest find was announced at the Potteries museum in Stoke-on-Trent, which has a major exhibition on the original hoard. The finds were made last month, with gold apparently brought to the surface by ploughing.

The original hoard was bought by Birmingham and Stoke-on-Trent museums for £3.3m with a substantial grant from the National Heritage Memorial Fund and donations from all over the world. Some of the pieces have toured the US and been viewed by more than 1m people.