Residents have already described to the BBC how lorries could be seen delivering materials, including fencing and septic tanks, after sundown on Friday.
The Conservative MP for the area, former Home Secretary James Cleverly, accused the travellers of “gaming the system”.
Campaigner Sherrie Smith, who founded Gypsy and Travellers Essex, pointed out that people felt they had no choice but to build plots unlawfully and then seek retrospective planning permission later.
According to council meeting papers from December, external, 35 traveller pitches were needed across the district.
Essex Police has been contacted for comment.