This is the heartbreaking moment police discovered a terrified group of baby spider monkeys crammed into storage boxes in the luggage compartment of a bus in Mexico.

The young primates, some looking just days old, huddle together for protection in the plastic boxes as they sit on wood shavings.

There is no sign of food or water and their only air comes from holes drilled in the sides of the boxes.

All the 20 monkeys have been placed in a shelter while vets and experts care for them, reports local media.

Mexico's Federal Environmental Protection Agency (Profepa) said the monkeys were found on a packed bus about to leave Dos Bocas, Chiapas.

Ten of the primates, they added, were babies and all of them were already showing signs of stress and dehydration.

Profepa said in a statement on December 9: 'The Profepa in Chiapas secured 20 spider monkeys that were transported in precarious conditions.

'Ten juvenile specimens and ten infants were identified.

'In response to a call from Dos Bocas customs personnel in Catazaja, Profepa went to verify a bus heading to Tabasco.

'In the trunk, two plastic boxes containing a total of 20 spider monkeys (Ateles geoffroyi) were observed.

'Unfortunately, the specimens showed signs of dehydration and stress, so they were immediately transferred to receive medical attention.

'The species 'Ateles geoffroyi' is classified as Endangered (P) according to NOM-059 and its commercialisation is prohibited by the General Wildlife Law.'

The deforestation related to illegal trafficking leads to habitat loss of the species in addition to pet trade and heavy pressure to hunting.

It is currently unknown whether someone has been arrested for the wildlife trafficking attempt.

Spider monkeys live naturally in the tropical rainforests all over South and Central America.