After observing for five minutes carefully, Zhang Yean shook her head in disappointment.
"The surface here is too rough to leave any fingerprint traces."
Jiang An removed his mask and sniffed the area where the oil residue was.
"I can't tell what kind of oil it is just by using my nose."
Then Zhang Yean and Wan both held the steel bar close to their mouths and sniffed it.
"It seems to have been exposed to the outdoors for a long time, and the oil has evaporated."
Jiang An asked, "Mr. Li, do we have the means to identify the type of oil in Jiangcheng City?"
"I'm not sure about this kind of special substance identification."
"We'll have to check with the Environmental Protection Bureau or the Food and Drug Administration."
Jiang An added, "If we have the capability to conduct oil component analysis, it would help us profile the perpetrator."
"No problem!"
