MACC investigation director Datuk Azam Baki said the six, aged between 30 to 50 including a woman, were instructed to be present at the MACC office this morning.
"They were released after giving their statements and inspections were made at their homes and offices," Azam told Bernama.
Azam said some of them were suspected to be involved in selling mineral ore transfer documents or Form Borang 13D illegally to miners without license.
The form, which is called a docket by the locals, is issued by the department with a payment of RM1 but MACC investigation revealed the form is being sold at a price of between RM150 and RM200 each.
To date, MACC has arrested seven individuals, including a senior officer and three of the department's officials, suspected of receiving bribes from the illegal bauxite mining operators.
Three others arrested, included a woman, are believed to be the 'middlemen' in the sales of Form 13D, which has to be kept by the lorry driver during the tranporting of the mineral. - Bernama