  Intriguing work on observations of 4.83 GHz formaldehyde (H2CO) absorptions
and 4.87 GHz H110a radio recombination lines (RRLs) towards 6.7 GHz methanol
(CH3OH) maser sources is presented. Methanol masers provide ideal sites to
probe the earliest stages of massive star formation, while 4.8 GHz formaldehyde
absorptions are accurate probes of physical conditions in dense $(10^{3} -
10^{5} cm^{-3})$ and low temperature molecular clouds towards massive star
forming regions. The work is aimed at studying feature similarities between the
formaldehyde absorptions and the methanol masers so as to expand knowledge of
events and physical conditions in massive star forming regions. A total of 176
methanol maser sources were observed for formaldehyde absorptions, and
formaldehyde absorptions were detected 138 of them. 53 of the formaldehyde
absorptions were newly detected. We noted a poor correlation between the
methanol and formaldehyde intensities, an indication that the signals (though
arise from about the same regions) are enhanced by different mechanisms. Our
results show higher detection rates of the formaldehyde lines for sources with
stronger methanol signals. The strongest formaldehyde absorptions were
associated with IRAS sources and IRDCs that have developed HII regions, and
that do not have EGOs.
