Hello Govindappa; Can your lab afford an endoscope? Whether that is a reasonable tool would depend on the diameter of the burrows you want to view. Best regards, Jim Des Lauriers
Endoscopes can be purchased very cheaply - some are used as tools to help mechanics and plumbers - they are not medical devices. I saw one for < $30 USD online. Make sure that these work in the near infra-red. Avoid visible light. It's easy to modify them. Ground penetrating radar can be used to map burrows. Best of luck with it. C