By Michael Bristow
BBC News, Beijing
China's government protested when these bronze heads went on sale earlier this year
China is planning to send teams of experts to the United States, Europe and Asia to find looted treasure.
The teams will be looking for precious items stolen from Beijing's former Summer Palace nearly 150 years ago.
Chinese experts believe 1.5 million items could have been taken from the site, which was destroyed by British and French troops.
Over recent years, China has become increasingly active in its efforts to raise the issue of stolen treasures.
Long road home
The latest expedition abroad was announced by Chen Mingjie, the director of the former palace's management office.
He said the first team will be sent to the US, where they will scour museums, libraries and private collections.
Experts will also visit Europe - principally the UK and France - and search Chinese collections across Asia, particularly those in Japan.
"We don't really know how many relics were plundered, since the catalogue of treasure was burned during the catastrophe," the state-run China Daily newspaper reported Mr Chen as saying.
"But based on our rough calculations, about 1.5 million relics are housed in more than 200 museums in 47 countries," he added.
The ruins of the former Summer Palace form a park in Beijing
He told another Chinese newspaper that the aim of the mission was simply to work out what had been taken from the palace.
He said this project was not being carried out in order to get the foreign collections to give back the items.
"Because of many factors, the road we need to take to get back cultural relics that have been lost overseas is a long one," he told the Beijing News.
"We will continue to work hard, but getting them back will not be easy."
China set up a fund in 2002 with the aim of getting back stolen cultural treasures.
The fund's administrators use its resources to try to persuade overseas collectors and museums to give back items or buy them themselves when they are put up for sale.
Ruins on show
Stolen treasure is a sensitive subject in China because it reminds ordinary people of a period when the country was weak.
Most items were looted and taken abroad between 1840 to 1949 when China was invaded by a number of foreign powers.
Just how sensitive this issue is was revealed earlier year when two bronze animal-head statues - taken from the old Summer Palace - were put up for auction.
The statues were two of 12 that once made up an elaborate fountain at the former palace. There was anger from both the Chinese government and ordinary people when they went on sale.
China's leaders continue to remind their citizens about incidents like the destruction of the old Summer Palace, which was looted and then burnt down by a joint British and French force in 1860.
The European allies were at the time trying to persuade China to open up more of the country to Western trade.
The former palace is now a park, where visitors can still see some ruined palaces among the trees and lakes.
Visitors are given guided tours of the destruction and reminded just who did the damage.