National Police chief Gen. Badrodin Haiti doubted that the discovery of suspicious rice grains in regions was similar to the plastic rice found recently in Bekasi, West Java.
He said the police were currently working with the Trade Ministry and several labs to clarify the cases.
"We have received reports from residents suspecting that they found [plastic rice]. They said that the grains' surface was shiny, but had no lab tests to confirm that," Badrodin said on Monday after a meeting with Trade Minister Rachmat Gobel at the Jakarta Police headquarters.
Badrodin said that the police have formed a special team comprising officers from the National Police and local headquarters to probe the findings.
The plastic rice, which is suspected to be imported from China, created public fear following reports of fake rice being used by a porridge seller named Dewi Septiani in Mustika Jaya, Bekasi, West Java.
The artificial rice grains were blended with regular ones but later melted like plastic when cooked, causing worry among Bekasi residents.
A laboratory of state-owned survey company PT Superintending Company of Indonesia (Sucofindo) previously confirmed that the rice in Bekasi contained polyvinyl chloride (PVC) usually found in pipes, as well as a plasticizer chemical substance usually found in hydraulic tools and electric capacitors that could cause kidney, liver, lung problems and cancer if consumed.
Residents in Gunung Kidul, Yogyakarta; Jayapura, Papua; and Medan, North Sumatra, have also reported the presence of plastic rice in their areas.
Badrodin said the police would check all of the reports to confirm whether there was widespread distribution of the artificial rice.
The central government has been on high alert regarding the plastic rice findings.
Home Minister Tjahjo Kumolo suspected it was an attempt to sabotage the government while President Joko "Jokowi" Widodo said the motive behind the controversial rice distribution could not be profit.
The Food and Drug Monitoring Agency (BPOM) said it had delivered the results of lab tests on rice that it received from the police on Friday. The police, however, still refused to disclose the test results on Monday.
Badrodin said the police were still waiting for tests from more labs, such as Bogor Agricultural University (IPB) and the police's central forensics laboratory (Puslabfor).
Minister Rachmat said he was also sceptical about the findings in other regions.
"I visited regions last week and found out that such a case only happened in Bekasi," he said.
Rachmat, who has just returned from the 2015 APEC Ministers Responsible for Trade Meeting (MRT) on Boracay Island, the Philippines, added that reports of plastic rice were once heard in Malaysia but no actual cases were taken to court as it was only a rumour created by certain individuals.
He said he had also asked for help from the Chinese government to identify the rice producer.
China has promised to help Indonesia solve the case, after a bilateral meeting with Chinese vice minister of commerce Wang Shouwen.
According to Wang, there is only one Chinese state-owned company that has a permit to export rice to Indonesia, making an examination into the matter easier.