In a twist to the lucrative criminal growth industry of indoor marijuana crops, two men have admitted using heat-detection cameras to locate and remove plants from suburban houses.

A Melbourne court heard that Danny Joe Szabo and Jano Matar used FLIRs - forward looking infrared radiometers - to detect "heat emitted from residences in the growing process".

Prosecutor Hayley Bate said that FLIR heat detection guns were "commonly used to locate a (marijuana) grow house emitting a strong heat signature".

Ms Bate said police intercepted calls between the pair that revealed marijuana was being located by identifying the location of "grow houses".

Ms Bate told Melbourne Magistrates Court this week that in a call on November 18 last year Szabo questioned Matar about using a "gun" the previous night and was told that there are "pictures" and "old ones" and "it showed us".